Imperfect Images
No telescope can form a perfect image. Even if a reflecting telescope could have a perfect mirror, or a refracting telescope could have a perfect lens, the effects of aperture diffraction are unavoidable. In reality, perfect mirrors and perfect lenses do not exist, so image aberrations in addition to aperture diffraction must be taken into account. Image aberrations can be broken down into two main classes, monochromatic, and polychromatic. In 1857, Philipp Ludwig von Seidel (1821–1896) decomposed the first order monochromatic aberrations into five constituent aberrations. They are now commonly referred to as the five Seidel Aberrations.
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Famous quotes containing the words imperfect and/or images:
“Behind every individual closes organization; before him opens liberty,—the Better, the Best. The first and worse races are dead. The second and imperfect races are dying out, or remain for the maturing of the higher. In the latest race, in man, every generosity, every new perception, the love and praise he extorts from his fellows, are certificates of advance out of fate into freedom.”
—Ralph Waldo Emerson (1803–1882)
“How clean the sun when seen in its idea,
Washed in the remotest cleanliness of a heaven
That has expelled us and our images . . .
The death of one god is the death of all.
Let purple Phoebus lie in umber harvest,
Let Phoebus slumber and die in autumn umber....”
—Wallace Stevens (1879–1955)